Skip Header

You are using a version of browser that may not display all the features of this website. Please consider upgrading your browser.
Protein

HTH-type transcriptional repressor PurR

Gene

purR

Organism
Escherichia coli (strain K12)
Status
Reviewed-Annotation score: Annotation score: 5 out of 5-Experimental evidence at protein leveli

Functioni

Is the main repressor of the genes involved in the de novo synthesis of purine nucleotides, regulating purB, purC, purEK, purF, purHD, purL, purMN and guaBA expression. In addition, it participates in the regulation or coregulation of genes involved in de novo pyrimidine nucleotide biosynthesis, salvage and uptake (pyrC, pyrD, carAB and codBA), and of several genes encoding enzymes necessary for nucleotide and polyamine biosynthesis (prsA, glyA, gcvTHP, speA, glnB). Binds to a 16-bp palindromic sequence located within the promoter region of pur regulon genes. The consensus binding sequence is 5'-ACGCAAACGTTTTCNT-3'. PurR is allosterically activated to bind its cognate DNA by binding the purine corepressors, hypoxanthine or guanine, thereby effecting transcription repression.4 Publications

Pathwayi: purine nucleotide biosynthesis

This protein regulates the pathway purine nucleotide biosynthesis, which is part of Purine metabolism.
View all proteins of this organism that are known to be involved in the pathway purine nucleotide biosynthesis and in Purine metabolism.

Sites

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Binding sitei73 – 731Corepressor
Binding sitei190 – 1901Corepressor
Sitei190 – 1901Is the key determinant of 6-oxopurine corepressor specificity
Binding sitei192 – 1921Corepressor
Binding sitei221 – 2211Corepressor
Binding sitei275 – 2751Corepressor

Regions

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
DNA bindingi4 – 2320H-T-H motifAdd
BLAST
DNA bindingi48 – 569

GO - Molecular functioni

  • DNA binding Source: EcoCyc
  • transcription factor activity, sequence-specific DNA binding Source: InterPro

GO - Biological processi

Complete GO annotation...

Keywords - Molecular functioni

Repressor

Keywords - Biological processi

Purine biosynthesis, Transcription, Transcription regulation

Keywords - Ligandi

DNA-binding

Enzyme and pathway databases

BioCyciEcoCyc:PD00219.
ECOL316407:JW1650-MONOMER.
MetaCyc:PD00219.
UniPathwayiUPA00488.

Names & Taxonomyi

Protein namesi
Recommended name:
HTH-type transcriptional repressor PurR
Alternative name(s):
Pur regulon repressor
Purine nucleotide synthesis repressor
Gene namesi
Name:purR
Ordered Locus Names:b1658, JW1650
OrganismiEscherichia coli (strain K12)
Taxonomic identifieri83333 [NCBI]
Taxonomic lineageiBacteriaProteobacteriaGammaproteobacteriaEnterobacterialesEnterobacteriaceaeEscherichia
Proteomesi
  • UP000000318 Componenti: Chromosome
  • UP000000625 Componenti: Chromosome

Organism-specific databases

EcoGeneiEG10800. purR.

Subcellular locationi

GO - Cellular componenti

  • cytosol Source: EcoCyc
Complete GO annotation...

Pathology & Biotechi

Mutagenesis

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Mutagenesisi54 – 541L → M: Slight decrease in operator DNA affinity.
Mutagenesisi55 – 551K → A: Decrease in operator DNA affinity. 1 Publication
Mutagenesisi147 – 1471W → A: 14-fold increase in corepressor affinity. Large increase in repressor activity. 1 Publication
Mutagenesisi147 – 1471W → F: Large decrease in corepressor affinity and in repressor activity. 1 Publication
Mutagenesisi147 – 1471W → R: 8-fold increase in corepressor affinity. Large increase in repressor activity. 1 Publication
Mutagenesisi190 – 1901R → A: Functional repressor. Corepressor specificity is expanded since it allows binding of adenine and 6-methylpurine. 1 Publication
Mutagenesisi190 – 1901R → Q: Functional repressor. Corepressor specificity is expanded since it allows binding of adenine. 1 Publication

PTM / Processingi

Molecule processing

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Initiator methionineiRemoved1 Publication
Chaini2 – 341340HTH-type transcriptional repressor PurRPRO_0000107976Add
BLAST

Proteomic databases

PaxDbiP0ACP7.
PRIDEiP0ACP7.

Expressioni

Inductioni

Negatively autoregulated.1 Publication

Interactioni

Subunit structurei

Homodimer.6 Publications

Binary interactionsi

WithEntry#Exp.IntActNotes
yebVP645034EBI-1115258,EBI-9126792

Protein-protein interaction databases

BioGridi4260271. 3 interactions.
DIPiDIP-35931N.
IntActiP0ACP7. 8 interactions.
STRINGi511145.b1658.

Structurei

Secondary structure

1
341
Legend: HelixTurnBeta strand
Show more details
Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Helixi4 – 118Combined sources
Beta strandi12 – 143Combined sources
Helixi15 – 228Combined sources
Helixi30 – 4213Combined sources
Helixi49 – 568Combined sources
Beta strandi61 – 677Combined sources
Beta strandi69 – 713Combined sources
Helixi72 – 8817Combined sources
Beta strandi91 – 966Combined sources
Helixi101 – 11313Combined sources
Beta strandi117 – 1226Combined sources
Helixi128 – 1369Combined sources
Turni137 – 1393Combined sources
Beta strandi142 – 1465Combined sources
Beta strandi152 – 1543Combined sources
Beta strandi156 – 1605Combined sources
Helixi162 – 17514Combined sources
Beta strandi180 – 1845Combined sources
Helixi195 – 20612Combined sources
Helixi213 – 2153Combined sources
Helixi223 – 23412Combined sources
Beta strandi236 – 2383Combined sources
Beta strandi241 – 2466Combined sources
Helixi248 – 26013Combined sources
Turni265 – 2684Combined sources
Beta strandi270 – 2756Combined sources
Helixi280 – 2823Combined sources
Beta strandi283 – 2853Combined sources
Beta strandi288 – 2914Combined sources
Helixi295 – 31016Combined sources
Beta strandi318 – 3214Combined sources
Beta strandi324 – 3263Combined sources
Helixi337 – 3393Combined sources

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
EntryMethodResolution (Å)ChainPositionsPDBsum
1BDHX-ray2.70A2-341[»]
1BDIX-ray3.00A2-341[»]
1DBQX-ray2.20A/B53-341[»]
1JFSX-ray2.90A2-341[»]
1JFTX-ray2.50A2-341[»]
1JH9X-ray2.55A2-341[»]
1JHZX-ray2.40A/B53-341[»]
1PNRX-ray2.70A2-341[»]
1PRUNMR-A1-56[»]
1PRVNMR-A1-56[»]
1QP0X-ray2.90A2-341[»]
1QP4X-ray3.00A2-341[»]
1QP7X-ray2.90A2-341[»]
1QPZX-ray2.50A2-341[»]
1QQAX-ray3.00A2-341[»]
1QQBX-ray2.70A2-341[»]
1VPWX-ray2.70A2-341[»]
1WETX-ray2.60A2-341[»]
1ZAYX-ray2.70A2-341[»]
2PUAX-ray2.90A2-341[»]
2PUBX-ray2.70A2-341[»]
2PUCX-ray2.60A2-341[»]
2PUDX-ray2.60A2-341[»]
2PUEX-ray2.70A2-341[»]
2PUFX-ray3.00A2-341[»]
2PUGX-ray2.70A2-341[»]
ProteinModelPortaliP0ACP7.
SMRiP0ACP7. Positions 2-340.
ModBaseiSearch...
MobiDBiSearch...

Miscellaneous databases

EvolutionaryTraceiP0ACP7.

Family & Domainsi

Domains and Repeats

Feature keyPosition(s)LengthDescriptionGraphical viewFeature identifierActions
Domaini2 – 5655HTH lacI-typeAdd
BLAST

Domaini

Consists of two structural and functional domains: an N-terminal DNA-binding domain, approximately the first 60 residues, and a larger C-terminal domain, approximately 280 residues, which imparts the function of corepressor binding and oligomerization.

Sequence similaritiesi

Phylogenomic databases

eggNOGiENOG4105ETE. Bacteria.
COG1609. LUCA.
HOGENOMiHOG000220180.
InParanoidiP0ACP7.
KOiK03604.
OMAiCSEYPES.
OrthoDBiEOG6SJJMM.
PhylomeDBiP0ACP7.

Family and domain databases

Gene3Di1.10.260.40. 1 hit.
HAMAPiMF_01277. HTH_type_PurR.
InterProiIPR000843. HTH_LacI.
IPR010982. Lambda_DNA-bd_dom.
IPR028082. Peripla_BP_I.
IPR023588. Tscrpt_reg_HTH_PurR.
[Graphical view]
PfamiPF00356. LacI. 1 hit.
[Graphical view]
PRINTSiPR00036. HTHLACI.
SMARTiSM00354. HTH_LACI. 1 hit.
[Graphical view]
SUPFAMiSSF47413. SSF47413. 1 hit.
SSF53822. SSF53822. 1 hit.
PROSITEiPS00356. HTH_LACI_1. 1 hit.
PS50932. HTH_LACI_2. 1 hit.
[Graphical view]

Sequencei

Sequence statusi: Complete.

Sequence processingi: The displayed sequence is further processed into a mature form.

P0ACP7-1 [UniParc]FASTAAdd to basket

« Hide

        10         20         30         40         50
MATIKDVAKR ANVSTTTVSH VINKTRFVAE ETRNAVWAAI KELHYSPSAV
60 70 80 90 100
ARSLKVNHTK SIGLLATSSE AAYFAEIIEA VEKNCFQKGY TLILGNAWNN
110 120 130 140 150
LEKQRAYLSM MAQKRVDGLL VMCSEYPEPL LAMLEEYRHI PMVVMDWGEA
160 170 180 190 200
KADFTDAVID NAFEGGYMAG RYLIERGHRE IGVIPGPLER NTGAGRLAGF
210 220 230 240 250
MKAMEEAMIK VPESWIVQGD FEPESGYRAM QQILSQPHRP TAVFCGGDIM
260 270 280 290 300
AMGALCAADE MGLRVPQDVS LIGYDNVRNA RYFTPALTTI HQPKDSLGET
310 320 330 340
AFNMLLDRIV NKREEPQSIE VHPRLIERRS VADGPFRDYR R
Length:341
Mass (Da):38,175
Last modified:January 23, 2007 - v2
Checksum:i5D1DA7CA6C72FBBC
GO

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
J04212 Genomic DNA. Translation: AAA24457.1.
X51368 Genomic DNA. Translation: CAA35753.1.
U00096 Genomic DNA. Translation: AAC74730.1.
AP009048 Genomic DNA. Translation: BAA15424.1.
PIRiA32027. RPECDU.
RefSeqiNP_416175.1. NC_000913.3.
WP_000190982.1. NZ_LN832404.1.

Genome annotation databases

EnsemblBacteriaiAAC74730; AAC74730; b1658.
BAA15424; BAA15424; BAA15424.
GeneIDi945226.
KEGGiecj:JW1650.
eco:b1658.
PATRICi32118622. VBIEscCol129921_1731.

Cross-referencesi

Sequence databases

Select the link destinations:
EMBLi
GenBanki
DDBJi
Links Updated
J04212 Genomic DNA. Translation: AAA24457.1.
X51368 Genomic DNA. Translation: CAA35753.1.
U00096 Genomic DNA. Translation: AAC74730.1.
AP009048 Genomic DNA. Translation: BAA15424.1.
PIRiA32027. RPECDU.
RefSeqiNP_416175.1. NC_000913.3.
WP_000190982.1. NZ_LN832404.1.

3D structure databases

Select the link destinations:
PDBei
RCSB PDBi
PDBji
Links Updated
EntryMethodResolution (Å)ChainPositionsPDBsum
1BDHX-ray2.70A2-341[»]
1BDIX-ray3.00A2-341[»]
1DBQX-ray2.20A/B53-341[»]
1JFSX-ray2.90A2-341[»]
1JFTX-ray2.50A2-341[»]
1JH9X-ray2.55A2-341[»]
1JHZX-ray2.40A/B53-341[»]
1PNRX-ray2.70A2-341[»]
1PRUNMR-A1-56[»]
1PRVNMR-A1-56[»]
1QP0X-ray2.90A2-341[»]
1QP4X-ray3.00A2-341[»]
1QP7X-ray2.90A2-341[»]
1QPZX-ray2.50A2-341[»]
1QQAX-ray3.00A2-341[»]
1QQBX-ray2.70A2-341[»]
1VPWX-ray2.70A2-341[»]
1WETX-ray2.60A2-341[»]
1ZAYX-ray2.70A2-341[»]
2PUAX-ray2.90A2-341[»]
2PUBX-ray2.70A2-341[»]
2PUCX-ray2.60A2-341[»]
2PUDX-ray2.60A2-341[»]
2PUEX-ray2.70A2-341[»]
2PUFX-ray3.00A2-341[»]
2PUGX-ray2.70A2-341[»]
ProteinModelPortaliP0ACP7.
SMRiP0ACP7. Positions 2-340.
ModBaseiSearch...
MobiDBiSearch...

Protein-protein interaction databases

BioGridi4260271. 3 interactions.
DIPiDIP-35931N.
IntActiP0ACP7. 8 interactions.
STRINGi511145.b1658.

Proteomic databases

PaxDbiP0ACP7.
PRIDEiP0ACP7.

Protocols and materials databases

Structural Biology KnowledgebaseSearch...

Genome annotation databases

EnsemblBacteriaiAAC74730; AAC74730; b1658.
BAA15424; BAA15424; BAA15424.
GeneIDi945226.
KEGGiecj:JW1650.
eco:b1658.
PATRICi32118622. VBIEscCol129921_1731.

Organism-specific databases

EchoBASEiEB0793.
EcoGeneiEG10800. purR.

Phylogenomic databases

eggNOGiENOG4105ETE. Bacteria.
COG1609. LUCA.
HOGENOMiHOG000220180.
InParanoidiP0ACP7.
KOiK03604.
OMAiCSEYPES.
OrthoDBiEOG6SJJMM.
PhylomeDBiP0ACP7.

Enzyme and pathway databases

UniPathwayiUPA00488.
BioCyciEcoCyc:PD00219.
ECOL316407:JW1650-MONOMER.
MetaCyc:PD00219.

Miscellaneous databases

EvolutionaryTraceiP0ACP7.
PROiP0ACP7.

Family and domain databases

Gene3Di1.10.260.40. 1 hit.
HAMAPiMF_01277. HTH_type_PurR.
InterProiIPR000843. HTH_LacI.
IPR010982. Lambda_DNA-bd_dom.
IPR028082. Peripla_BP_I.
IPR023588. Tscrpt_reg_HTH_PurR.
[Graphical view]
PfamiPF00356. LacI. 1 hit.
[Graphical view]
PRINTSiPR00036. HTHLACI.
SMARTiSM00354. HTH_LACI. 1 hit.
[Graphical view]
SUPFAMiSSF47413. SSF47413. 1 hit.
SSF53822. SSF53822. 1 hit.
PROSITEiPS00356. HTH_LACI_1. 1 hit.
PS50932. HTH_LACI_2. 1 hit.
[Graphical view]
ProtoNetiSearch...

Publicationsi

« Hide 'large scale' publications
  1. "Escherichia coli gene purR encoding a repressor protein for purine nucleotide synthesis. Cloning, nucleotide sequence, and interaction with the purF operator."
    Rolfes R.J., Zalkin H.
    J. Biol. Chem. 263:19653-19661(1988) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA].
  2. "Autoregulation of PurR repressor synthesis and involvement of purR in the regulation of purB, purC, purL, purMN and guaBA expression in Escherichia coli."
    Meng L.M., Kilstrup M., Nygaard P.
    Eur. J. Biochem. 187:373-379(1990) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [GENOMIC DNA], FUNCTION, INDUCTION.
    Strain: K12.
  3. Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
    Strain: K12 / W3110 / ATCC 27325 / DSM 5911.
  4. Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
    Strain: K12 / MG1655 / ATCC 47076.
  5. "Highly accurate genome sequences of Escherichia coli K-12 strains MG1655 and W3110."
    Hayashi K., Morooka N., Yamamoto Y., Fujita K., Isono K., Choi S., Ohtsubo E., Baba T., Wanner B.L., Mori H., Horiuchi T.
    Mol. Syst. Biol. 2:E1-E5(2006) [PubMed] [Europe PMC] [Abstract]
    Cited for: NUCLEOTIDE SEQUENCE [LARGE SCALE GENOMIC DNA].
    Strain: K12 / W3110 / ATCC 27325 / DSM 5911.
  6. "Purification of the Escherichia coli purine regulon repressor and identification of corepressors."
    Rolfes R.J., Zalkin H.
    J. Bacteriol. 172:5637-5642(1990) [PubMed] [Europe PMC] [Abstract]
    Cited for: PROTEIN SEQUENCE OF 2-7, FUNCTION, IDENTIFICATION OF COREPRESSORS.
  7. "Structural characterization and corepressor binding of the Escherichia coli purine repressor."
    Choi K.Y., Zalkin H.
    J. Bacteriol. 174:6207-6214(1992) [PubMed] [Europe PMC] [Abstract]
    Cited for: PARTIAL PROTEIN SEQUENCE, FUNCTION, CHARACTERIZATION, SUBUNIT.
  8. "Biosynthesis of purine nucleotides."
    Zalkin H., Nygaard P.
    (In) Neidhardt F.C., Curtiss R. III, Ingraham J.L., Lin E.C.C., Low K.B. Magasanik B., Reznikoff W.S., Riley M., Schaechter M., Umbarger H.E. (eds.); Escherichia coli and Salmonella: Cellular and molecular biology (2nd ed.), pp.561-579, American Society for Microbiology Press, Washington D.C. (1996)
    Cited for: REVIEW.
  9. "Purine and pyrimidine-specific repression of the Escherichia coli carAB operon are functionally and structurally coupled."
    Devroede N., Thia-Toong T.-L., Gigot D., Maes D., Charlier D.
    J. Mol. Biol. 336:25-42(2004) [PubMed] [Europe PMC] [Abstract]
    Cited for: FUNCTION IN CARAB REPRESSION.
  10. "Crystal structure of LacI member, PurR, bound to DNA: minor groove binding by alpha helices."
    Schumacher M.A., Choi K.Y., Zalkin H., Brennan R.G.
    Science 266:763-770(1994) [PubMed] [Europe PMC] [Abstract]
    Cited for: X-RAY CRYSTALLOGRAPHY (2.7 ANGSTROMS) IN COMPLEX WITH HYPOXANTHINE COREPRESSOR AND PURF OPERATOR DNA.
  11. "Mechanism of corepressor-mediated specific DNA binding by the purine repressor."
    Schumacher M.A., Choi K.Y., Lu F., Zalkin H., Brennan R.G.
    Cell 83:147-155(1995) [PubMed] [Europe PMC] [Abstract]
    Cited for: X-RAY CRYSTALLOGRAPHY (2.2 ANGSTROMS) OF 53-341.
  12. "Structural comparison of the free and DNA-bound forms of the purine repressor DNA-binding domain."
    Nagadoi A., Morikawa S., Nakamura H., Enari M., Kobayashi K., Yamamoto H., Sampei G., Mizobuchi K., Schumacher M.A., Brennan R.G., Nishimura Y.
    Structure 3:1217-1224(1995) [PubMed] [Europe PMC] [Abstract]
    Cited for: STRUCTURE BY NMR OF 1-56.
  13. "The X-ray structure of the PurR-guanine-purF operator complex reveals the contributions of complementary electrostatic surfaces and a water-mediated hydrogen bond to corepressor specificity and binding affinity."
    Schumacher M.A., Glasfeld A., Zalkin H., Brennan R.G.
    J. Biol. Chem. 272:22648-22653(1997) [PubMed] [Europe PMC] [Abstract]
    Cited for: X-RAY CRYSTALLOGRAPHY (2.6 ANGSTROMS) IN COMPLEX WITH GUANINE COREPRESSOR AND PURF OPERATOR DNA.
  14. "Structure-based redesign of corepressor specificity of the Escherichia coli purine repressor by substitution of residue 190."
    Lu F., Schumacher M.A., Arvidson D.N., Haldimann A., Wanner B.L., Zalkin H., Brennan R.G.
    Biochemistry 37:971-982(1998) [PubMed] [Europe PMC] [Abstract]
    Cited for: X-RAY CRYSTALLOGRAPHY (2.6 ANGSTROMS) OF MUTANTS GLN-190 AND ALA-190 IN COMPLEXES WITH VARIOUS PURINES AND OPERATOR DNA, MUTAGENESIS OF ARG-190.
  15. "The structure of PurR mutant L54M shows an alternative route to DNA kinking."
    Arvidson D.N., Lu F., Faber C., Zalkin H., Brennan R.G.
    Nat. Struct. Biol. 5:436-441(1998) [PubMed] [Europe PMC] [Abstract]
    Cited for: X-RAY CRYSTALLOGRAPHY (2.7 ANGSTROMS) OF MUTANT MET-54 IN COMPLEX WITH HYPOXANTHINE COREPRESSOR AND PURF OPERATOR DNA.
  16. "The role of lysine 55 in determining the specificity of the purine repressor for its operators through minor groove interactions."
    Glasfeld A., Koehler A.N., Schumacher M.A., Brennan R.G.
    J. Mol. Biol. 291:347-361(1999) [PubMed] [Europe PMC] [Abstract]
    Cited for: X-RAY CRYSTALLOGRAPHY (2.5 ANGSTROMS) OF WILD-TYPE AND MUTANT ALA-55 IN COMPLEXES WITH VARIOUS PURF OPERATOR ANALOGS, MUTAGENESIS OF LYS-55.
  17. "The roles of exocyclic groups in the central base-pair step in modulating the affinity of PurR for its operator."
    Zheleznova E.E., Brennan R.G.
    Submitted (DEC-1999) to the PDB data bank
    Cited for: X-RAY CRYSTALLOGRAPHY (2.7 ANGSTROMS) IN COMPLEX WITH HYPOXANTHINE COREPRESSOR AND PURF OPERATOR ANALOG.
  18. "Role of residue 147 in the gene regulatory function of the Escherichia coli purine repressor."
    Huffman J.L., Lu F., Zalkin H., Brennan R.G.
    Biochemistry 41:511-520(2002) [PubMed] [Europe PMC] [Abstract]
    Cited for: X-RAY CRYSTALLOGRAPHY (2.4 ANGSTROMS) OF MUTANTS ARG-147; PHE-147 AND ALA-147 UNCOMPLEXED AND IN COMPLEX WITH HYPOXANTHINE COREPRESSOR AND PURF OPERATOR DNA, MUTAGENESIS OF TRP-147.

Entry informationi

Entry nameiPURR_ECOLI
AccessioniPrimary (citable) accession number: P0ACP7
Secondary accession number(s): P15039, Q83RB1
Entry historyi
Integrated into UniProtKB/Swiss-Prot: November 22, 2005
Last sequence update: January 23, 2007
Last modified: July 6, 2016
This is version 94 of the entry and version 2 of the sequence. [Complete history]
Entry statusiReviewed (UniProtKB/Swiss-Prot)
Annotation programProkaryotic Protein Annotation Program

Miscellaneousi

Miscellaneous

The corepressors hypoxanthine and guanine bind cooperatively to single PurR sites in each subunit of the dimer, inducing a conformational change which increases the affinity of PurR for its DNA operator sites.

Keywords - Technical termi

3D-structure, Complete proteome, Direct protein sequencing, Reference proteome

Documents

  1. Escherichia coli
    Escherichia coli (strain K12): entries and cross-references to EcoGene
  2. PATHWAY comments
    Index of metabolic and biosynthesis pathways
  3. PDB cross-references
    Index of Protein Data Bank (PDB) cross-references
  4. SIMILARITY comments
    Index of protein domains and families

Similar proteinsi

Links to similar proteins from the UniProt Reference Clusters (UniRef) at 100%, 90% and 50% sequence identity:
100%UniRef100 combines identical sequences and sub-fragments with 11 or more residues from any organism into one UniRef entry.
90%UniRef90 is built by clustering UniRef100 sequences that have at least 90% sequence identity to, and 80% overlap with, the longest sequence (a.k.a seed sequence).
50%UniRef50 is built by clustering UniRef90 seed sequences that have at least 50% sequence identity to, and 80% overlap with, the longest sequence in the cluster.